1. Field of the Invention:
The present invention relates to a method of and an apparatus for supplying a coating agent such as a sealant to a coating robot such as a sealing robot which applies the coating agent to required portions of an article conveyed on a conveyor line.
2. Description of the Relevant Art:
During assembly of various articles such as automotive bodies, for example, many portions or areas of such articles have to be sealed to make airtight and liquidtight the mating edges of panels which are joined together as by spot welding. Sealing the innermost area of an engine compartment, in particular, has resulted in various problems. The process of sealing that area is complex, but the area has to be sealed quickly. The manual sealing procedure is subject to limitations.
In view of the above drawbacks, there has recently been proposed a sealing robot disposed on a conveyor line and having a sealing gun for automatically carrying out a sealing process, the sealing robot being operable for sealing an article according to a working program (see Japanese Laid-Open Patent Publication No. 55-81759 published June 20, 1980).
The sealing robot is supplied with a sealant by a fixed-displacement sealant supply pump during the sealing process. In the event that the outlet side of the pump fails to discharge the sealant due for example to a clog, and undue pressure buildup is developed in the pipe connected to the pump outlet, and hence the pump and pipes and devices coupled thereto may be damaged. If the inlet side of the pump fails to deliver the sealant to the pump, the pump operates idly and may be damaged. Should the pipes remain pressurized after a sealing procedure has been completed, the sealant in the pipes would be solidified. To prevent this, the pipes should be relieved of any remaining pressure subsequent to the sealing process.
Another problem with the conventional sealing robot is that when the sealing robot is to be slowed down to change its direction of movement during a sealing operation or when the rate of discharge of the sealant from the pump is varied due to aging of the viscosity of the sealant, the amount of the sealant coated on the article per unit distance that the sealing robot has traversed is also varied, with the result that the sealant coat on the article becomes irregular. This problem manifests itself and should be solved especially when sealing the joined edges (joined lines) of panels which define an automotive engine compartment inasmuch as the joined edges are curved and the sealing robot moves at largely different speeds along the joined edges.
The present invention has been made in view of the aforesaid problems.